Sweden's ZigBee City

In 2004, the Swedish government began drafting new legislation that prompted Göteborg Energi (GE) to start considering different solutions for remote meter reading. At that time, the only developed solutions were based on either power line carrier (PLC) or, to a lesser extent, radio on proprietary or restricted frequencies. The investment cost for a relatively small undertaking of a project of this nature would be substantial, even considering the opportunity to drastically reduce the number of staff involved in manual meter reading. Even if the simplest and cheapest solution were selected, the return on investment would be poor and the overall return would be negative.

However, in 2006, the management team of GE made a bold decision. Forced by new legislation to implement advanced metering infrastructure (AMI), the team decided to examine, in detail, existing and new technologies available for automated meter reading. The team had to make a strategic decision: either adopt the cheapest possible system just to adhere to the new legislation, or seek greater savings and extra revenue to warrant investment in a more advanced system. The older proven technologies did not meet the performance levels demanded. Furthermore, the potential for a long life span was diminished. GE decided to make the most of its investment and look for the most advanced system available at a reasonable cost.

It was a brave decision when GE awarded a contract to a supplier that had no prior installations in Europe, and to Prime, the company responsible for the implementation, which had no previous experience in undertaking such a huge project.

Göteborg Energi

Göteborg, GE's service territory, is the second-largest city in Sweden with a population of approximately 500,000. GE has supplied its customers with gas since 1846 and electricity since 1908. The utility also serves customers in the city with district heating, optical fibers and district cooling. Thus, GE is first and foremost a builder and caretaker of various forms of energy-related infrastructure. The AMI project would require the replacement of some 265,000 existing electricity meters.

The GE metering project team was given the task of finding the best system available at a reasonable cost. The contract also required the supplier to take on the responsibility of installing the 265,000 meters prior to July 2009, and managing and operating the system for a minimum of four years after the installation was complete.

The business case for the project was based on an estimated cost of approximately 200 euros (US$273) per installation, including investment and operational costs, and internal savings. The scrap value for the old meters was not included. To produce a positive business case over a period of 15 years, it was estimated an additional revenue of 1 euro (US$1.37) per customer per month would have to be received from the new services offered by AMI.

AMI System Selection Process

It was the view of GE's senior management that, to reap the real benefits of remote reading, readings must not only be monthly but, in the future, hourly. The shorter the time cycle between readings, the more useful the information is for the end user. Hourly readings provide a very different understanding of usage pattern than monthly or yearly readings. The more advanced metering systems also offered a much broader spectrum of possible services than those previously used. Hourly readings, on-demand readings in real time, remote connect/disconnect, power-failure alarm in real time, monitoring of power usage and voltage levels, and other advanced functionalities were among the features GE management anticipated.

The tendering process was initiated, and GE had received eight tenders by the end of 2006. The solutions offered covered all available means of communication available on the market as well as one new solution. Four suppliers supported PLC as the main form of communication, two had selected general packet radio service (GPRS), one suggested radio on a restricted frequency and one, the new entrant on the European market, had ZigBee as the main form of communication.

Internally, the project focus prior to the tendering procedure had been centered on which form of communication was best, the cheaper PLC or the more advanced GPRS. During the evaluation of the tenders, and in light of some of the problems other utilities had experienced with their chosen solutions, it became clear the key was really the central metering system at the heart of the different solutions.

Some of the systems were very basic and some were not beyond the design stage. The project team was surprised when one supplier offered the opportunity to become the first customer of its new system under development, but it was not the wish of the project team to become a guinea pig in developing a system from scratch.

Finally, it became clear one supplier had a system that was beyond the others in functionality, user friendliness and advanced thinking. The metering infrastructure was based on ZigBee as the main form of communication, which was very new at the time. There were no major ZigBee implementations for AMI in the world. The fact ZigBee was an open standard and the possibilities this presented were considerably alluring. The supplier also was able to present a smaller installation that used the system for gas and water metering, as well. This proved the system could handle multi-metering. The ZigBee system satisfied the GE objectives, and the utility decided to make the most of the investment by selecting the most advanced system available at a reasonable cost.

The Solution

The system chosen was Aimir, by Nuri Telecom of Korea. Nuri's partner, Embriq of Norway, was the contractual partner responsible for installation of the meters and infrastructure as well as operating the system for a minimum of four years, with a possible extension to eight years.

The infrastructure consists of 265,000 electrical meters that communicate through ZigBee with approximately 8,000 concentrators. At the initial phase of the project, it was estimated approximately 7,000 repeaters would be necessary to enhance the reach of the concentrators. In the end, only 20 repeaters were needed because of the advantage of the mesh network. GPRS or optical fiber is used to connect the concentrators to Aimir, the metering system. The single-phase meters were supplied by General Electric and the poly-phase meters by Aidon and Kamstrup.

ZigBee is an open standard in the United States on the 2,400-MHz to 2,483.5-MHz and 902-MHz to 928-MHz frequency bands. ZigBee uses the frequency band of 2,400 MHz to 2,483.5 MHz for the globally open standard. The higher frequency of 2.4 GHz means one must have a data rate of up to 250 kbps instead of 40 kbps in the 902-MHz to 928-MHz frequency band. The high spreading factor of 802.15.4 at 2.4 GHz and the 16 available channels empirically deliver disturbance-free networking, even on a citywide network. ZigBee networking also is self-healing, with route rediscovery if messages fail, which means local interference can be worked around. This has led to impressive performance attained in Göteborg, the first ZigBee city.

The ZigBee network is built up as a self-configuring mesh. This means if the signal is unable to find its usual route, it will jump on other ZigBee modules to find another route for communication. Each meter thus becomes a repeater, and the network becomes stronger the more ZigBee modules are installed. High reliability is achieved coupled with flexible routing. The reach of the ZigBee signal is stated to be below 250 m (820 ft) with free sight line, making ZigBee suitable for home automation. However, with the Nuri solution, a reach of more than 2,000 m (6,562 ft) is attained with free sight line, making ZigBee suitable for a totally different set of services and applications. The rather low bandwidth, of course, means ZigBee is no substitution for Wi-Fi and other broadband services. One of the main advantages of ZigBee is the low power consumption. The concentrators have a usage of only 3 W to 4 W, not much more than electrical meter consumption. A battery-operated ZigBee module — for example, for water metering — has a battery life exceeding five years.

The Project

In January 2008, GE undertook a pilot to prepare for the actual rollout. All the processes, hardware, software, integrations, staff involved and suppliers performed a dress rehearsal. This provided a thorough check of what needed to be corrected before full-scale implementation.

In March 2008, the large installation phase started. For a period of more than 15 months, approximately 70 electricians installed up to 1,500 meters per day. Appointments were planned in advance to access the meters of 42,000 customers. A separate call center was set up to handle these bookings and respond to questions regarding the installations. An extensive program for customer communication was undertaken to ensure all customers were informed about the project, the reason for it and the benefits for the end customers.

The most complex part of the project was the necessary data handling. A huge amount of information had to be collected from various systems on the customer side, cleaned and aggregated, and transferred to Prime in a controlled manner. The information created at each installation (for example, new meter identification, metering value and time for installation) had to be transferred back to the customer and then distributed in a timely manner to various systems such as the customer information system, billing system, meter data management system and so forth. To effectively handle all data, an installation system was created based on the business model for the rollout. This system made it possible to keep track of each and every individual installation, see when it was done, by whom and whether all the data was collected correctly, and when the meter installation was approved based on a set of predefined criteria.

By January 2010, more than 265,000 meters had been installed, the performance level for monthly reads was approximately 99.8%, 8,000 concentrators had been installed and the project entered the final clean-up phase. A couple hundred meters are not yet installed because of problems accessing the customer site. Of the installed meters, approximately 500 meters still need some work to communicate regularly with the concentrators. In some cases, they need an extra antenna, and in other cases, there are software issues or other problems.

Additional Functionalities

Apart from just collecting metering data, the metering system has several additional functionalities already in use. Remote connect and disconnect were the first so-called advanced metering management functionalities put to use. Hourly metering values are collected daily, but not yet used for billing purposes. The hourly readings are used in customer dialogues as well as for troubleshooting faulty equipment and abnormal usage among customers. On-demand readings are mainly used in the customer contact center. As the majority of customers do not have direct access to their meters, because the meters are frequently in group metering facilities in building basements, the ability to check current meter readings is valuable in discussions with customers.

Power failure real-time alarm, registration and statistics are all collected continuously. This creates an enormous amount of data that needs to be handled efficiently. The next step is to integrate the metering system with the supervisory control and data acquisition system to have a good overview of power failures on the low-voltage grid. This integration also will give the operator of the metering system the information needed in the event of power failures elsewhere on the grid or beyond GE's service territory.

Power quality, power usage and voltage level monitoring have proven valuable in customer dialogue and also will be used for better planning of investments and reinvestments in the grid. Also, by monitoring power quality at the substation level, weaknesses in the grid can be pinpointed and abnormal losses can be identified.

Multi-metering is the next logical step when an AMI has been implemented. GE is already implementing district heating meters with ZigBee communication, thus using the same infrastructure as for the electricity meters. Gas meters will be next to be equipped with a ZigBee module. They are already developed, and a smaller pilot project to secure all functionalities is planned for the future.

Creating New Business Opportunities

By using the new AMI, it is possible to add new services for customers. The opportunities for this were deemed so promising that GE formed a new business unit to effectively pursue the new possible businesses. Today, the first new services are being sold.

Many apartments in Sweden now have the cost of supplying hot and cold water as well as heat included in the rental terms. The cost is determined based on apartment size, not on actual usage. This does not encourage an efficient use of energy and is not always a fair cost practice. Owners of these apartment complexes can now buy distributed metering services from GE through which all consumption will be measured on an individual basis, and the metering values can be used by landlords to distribute costs based on actual energy consumption.

Another service about to start is the provision of fire and burglar alarms. This is yet another way of using the existing infrastructure. Radio locks remotely controlled in addition to street-lighting control by ZigBee also are among the new services being planned.

A Good Business Decision

The implementation of AMI is costly and time consuming. Apart from the logistical issue of the rollout, data handling proved to be the main concern. The extra investment of providing a more advanced system has proved to be a very good business decision. The more advanced system allows GE to provide many benefits, such as improved customer service and dialogue, improved monitoring of the low-voltage grid, improved quality of data for grid planning as well as opportunities for new customer services.

A new law that came into effect in Sweden in July 2009 states that all electricity customers in Sweden must be billed for actual usage and that the usage is to be presented per calendar month. In effect, this has rendered manual reading obsolete and made it necessary to install metering systems that can read the electricity meters remotely once a month. Therefore, GE's management deserves credit for the investment decisions taken in 2006 that satisfies and goes well beyond the requirements included in the 2009 legislation.

Today, GE's AMI project is regarded as a huge success. The performance levels are outstanding, 265,000 electricity meters were installed, a large number of advanced metering management functionalities were implemented, multi-metering is being installed on the same AMI and totally new services are being offered to customers based on this new technology. The vision of a ZigBee city has become a reality.

Tomas Arnewid (tomas.arnewid@goteborgenergi.se) is the project manager for the advanced metering infrastructure project at Göteborg Energi and is also helping utilities across Europe with the planning and implementation of smart metering projects. He is a senior management consultant with extensive experience in large, complex and often international projects. Arnewid is now a partner and co-founder of BlazeConsultants, a management consulting firm.

What is ZigBee?

ZigBee is a suite of high-level communication protocol specifications that enable the use of small, low-cost, low-power digital radios based on the IEEE 802.15.4-2003 standard for low-rate wireless personal area networks. Devices could include light switches with lamps, in-home displays and consumer electronics equipment. The technology defined by the ZigBee specification is intended to be simpler and less expensive than other solutions including Bluetooth. ZigBee is targeted at radio-frequency applications that require a low data rate, long battery life and secure networking.

Editor's note: The term ZigBee was inspired by the figure 8 (or zigzag) motion with which honey bees communicate the direction to the pollen source. ZigBee hops from one sender/receiver in a nonlinear fashion to transmit data.

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